239 research outputs found
FlashCam: A fully digital camera for CTA telescopes
The future Cherenkov Telescope Array (CTA) will consist of several tens of
telescopes of different mirror sizes. CTA will provide next generation
sensitivity to very high energy photons from few tens of GeV to >100 TeV.
Several focal plane instrumentation options are currently being evaluated
inside the CTA consortium. In this paper, the current status of the FlashCam
prototyping project is described. FlashCam is based on a fully digital camera
readout concept and features a clean separation between photon detector plane
and signal digitization/triggering electronics.Comment: In Proceedings of the 2012 Heidelberg Symposium on High Energy
Gamma-Ray Astronomy. All CTA contributions at arXiv:1211.184
The Optical System for the Large Size Telescope of the Cherenkov Telescope Array
The Large Size Telescope (LST) of the Cherenkov Telescope Array (CTA) is
designed to achieve a threshold energy of 20 GeV. The LST optics is composed of
one parabolic primary mirror 23 m in diameter and 28 m focal length. The
reflector dish is segmented in 198 hexagonal, 1.51 m flat to flat mirrors. The
total effective reflective area, taking into account the shadow of the
mechanical structure, is about 368 m. The mirrors have a sandwich structure
consisting of a glass sheet of 2.7 mm thickness, aluminum honeycomb of 60 mm
thickness, and another glass sheet on the rear, and have a total weight about
47 kg. The mirror surface is produced using a sputtering deposition technique
to apply a 5-layer coating, and the mirrors reach a reflectivity of 94%
at peak. The mirror facets are actively aligned during operations by an active
mirror control system, using actuators, CMOS cameras and a reference laser.
Each mirror facet carries a CMOS camera, which measures the position of the
light spot of the optical axis reference laser on the target of the telescope
camera. The two actuators and the universal joint of each mirror facet are
respectively fixed to three neighboring joints of the dish space frame, via
specially designed interface plate.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherlands. All CTA contributions at
arXiv:1508.0589
FlashCam: a fully-digital camera for the medium-sized telescopes of the Cherenkov Telescope Array
The FlashCam group is currently preparing photomultiplier-tube based cameras
proposed for the medium-sized telescopes (MST) of the Cherenkov Telescope Array
(CTA). The cameras are designed around the FlashCam readout concept which is
the first fully-digital readout system for Cherenkov cameras, based on
commercial FADCs and FPGAs as key components for the front-end electronics
modules and a high performance camera server as back-end. This contribution
describes the progress of the full-scale FlashCam camera prototype currently
under construction, as well as performance results also obtained with earlier
demonstrator setups. Plans towards the production and implementation of
FlashCams on site are also briefly presented.Comment: 8 pages, 6 figures. In Proceedings of the 34th International Cosmic
Ray Conference (ICRC2015), The Hague, The Netherlands. All CTA contributions
at arXiv:1508.0589
Performance Verification of the FlashCam Prototype Camera for the Cherenkov Telescope Array
The Cherenkov Telescope Array (CTA) is a future gamma-ray observatory that is
planned to significantly improve upon the sensitivity and precision of the
current generation of Cherenkov telescopes. The observatory will consist of
several dozens of telescopes with different sizes and equipped with different
types of cameras. Of these, the FlashCam camera system is the first to
implement a fully digital signal processing chain which allows for a traceable,
configurable trigger scheme and flexible signal reconstruction. As of autumn
2016, a prototype FlashCam camera for the medium-sized telescopes of CTA nears
completion. First results of the ongoing system tests demonstrate that the
signal chain and the readout system surpass CTA requirements. The stability of
the system is shown using long-term temperature cycling.Comment: 5 pages, 13 figures, Proceedings of the 9th International Workshop on
Ring Imaging Cherenkov Detectors (RICH 2016), Lake Bled, Sloveni
First Constraints from DAMIC-M on Sub-GeV Dark-Matter Particles Interacting with Electrons
We report constraints on sub-GeV dark matter particles interacting with electrons from the first underground operation of DAMIC-M detectors. The search is performed with an integrated exposure of 85.23 g days, and exploits the subelectron charge resolution and low level of dark current of DAMIC-M charge-coupled devices (CCDs). Dark-matter-induced ionization signals above the detector dark current are searched for in CCD pixels with charge up to 7e−. With this dataset we place limits on dark matter particles of mass between 0.53 and 1000 MeV/c2, excluding unexplored regions of parameter space in the mass ranges [1.6,1000] MeV/c2 and [1.5,15.1] MeV/c2 for ultralight and heavy mediator interactions, respectively
Innate and adaptive T cells in asthmatic patients: relationship to severity and disease mechanisms
BackgroundAsthma is a chronic inflammatory disease involving diverse cells and mediators whose interconnectivity and relationships to asthma severity are unclear.ObjectiveWe performed a comprehensive assessment of TH17 cells, regulatory T cells, mucosal-associated invariant T (MAIT) cells, other T-cell subsets, and granulocyte mediators in asthmatic patients.MethodsSixty patients with mild-to-severe asthma and 24 control subjects underwent detailed clinical assessment and provided induced sputum, endobronchial biopsy, bronchoalveolar lavage, and blood samples. Adaptive and invariant T-cell subsets, cytokines, mast cells, and basophil mediators were analyzed.ResultsSignificant heterogeneity of T-cell phenotypes was observed, with levels of IL-13–secreting T cells and type 2 cytokines increased at some, but not all, asthma severities. TH17 cells and ??-17 cells, proposed drivers of neutrophilic inflammation, were not strongly associated with asthma, even in severe neutrophilic forms. MAIT cell frequencies were strikingly reduced in both blood and lung tissue in relation to corticosteroid therapy and vitamin D levels, especially in patients with severe asthma in whom bronchoalveolar lavage regulatory T-cell numbers were also reduced. Bayesian network analysis identified complex relationships between pathobiologic and clinical parameters. Topological data analysis identified 6 novel clusters that are associated with diverse underlying disease mechanisms, with increased mast cell mediator levels in patients with severe asthma both in its atopic (type 2 cytokine–high) and nonatopic forms.ConclusionThe evidence for a role for TH17 cells in patients with severe asthma is limited. Severe asthma is associated with a striking deficiency of MAIT cells and high mast cell mediator levels. This study provides proof of concept for disease mechanistic networks in asthmatic patients with clusters that could inform the development of new therapies
The Cherenkov Telescope Array Large Size Telescope
The two arrays of the Very High Energy gamma-ray observatory Cherenkov
Telescope Array (CTA) will include four Large Size Telescopes (LSTs) each with
a 23 m diameter dish and 28 m focal distance. These telescopes will enable CTA
to achieve a low-energy threshold of 20 GeV, which is critical for important
studies in astrophysics, astroparticle physics and cosmology. This work
presents the key specifications and performance of the current LST design in
the light of the CTA scientific objectives.Comment: 4 pages, 5 figures, In Proceedings of the 33rd International Cosmic
Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at
arXiv:1307.223
Search for Daily Modulation of MeV Dark Matter Signals with DAMIC-M
Dark Matter (DM) particles with sufficiently large cross sections may scatter
as they travel through Earth's bulk. The corresponding changes in the DM flux
give rise to a characteristic daily modulation signal in detectors sensitive to
DM-electron interactions. Here, we report results obtained from the first
underground operation of the DAMIC-M prototype detector searching for such a
signal from DM with MeV-scale mass. A model-independent analysis finds no
modulation in the rate of 1 events with periods in the range 1-48 h. We
then use these data to place exclusion limits on DM in the mass range [0.53,
2.7] MeV/c interacting with electrons via a dark photon mediator. Taking
advantage of the time-dependent signal we improve by 2 orders of
magnitude on our previous limit obtained from the total rate of 1 events,
using the same data set. This daily modulation search represents the current
strongest limit on DM-electron scattering via ultralight mediators for DM
masses around 1 MeV/c
The DAMIC-M experiment: Status and first results
The DAMIC-M (DArk Matter In CCDs at Modane) experiment employs thick, fully depleted silicon charged-coupled devices (CCDs) to search for dark matter particles with a target exposure of 1 kg-year. A novel skipper readout implemented in the CCDs provides single electron resolution through multiple non-destructive measurements of the individual pixel charge, pushing the detection threshold to the eV-scale. DAMIC-M will advance by several orders of magnitude the exploration of the dark matter particle hypothesis, in particular of candidates pertaining to the so-called “hidden sector.” A prototype, the Low Background Chamber (LBC), with 20g of low background Skipper CCDs, has been recently installed at Laboratoire Souterrain de Modane and is currently taking data. We will report the status of the DAMIC-M experiment and first results obtained with LBC commissioning data
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